ehhm "Grüß Gott werter Herr" is how we welcome in Germany you can improve seal with it ;)
If you wanna make seal angry say things like "hundesohn" (very popluair in Germany) means son of a dog, "hurensohn" - son of a bitch, wixxer - wanker(or something like this), "Ich kote deiner Mutter ins Gesicht" I shit in your mothers face. "Dein Vater ist ein reudiger Salamander" Your father is a mangy salamander, "Du sohn eines besoffenen Schweines" Son of a drunken pig!